Guidewires are used in various medical procedures to position medical devices at desired locations within a patient's vascular system. Guidewires, which are steerable, are inserted and maneuvered through the patient's vasculature to a previously chosen location. Once in place, the guidewire provides the means to place a non-steerable device, such as an over the wire catheter, at the chosen body site. For example, a catheter is slid over the guidewire until the catheter, or some working portion thereof, is positioned within the vasculature at the desired location. Generally speaking, guidewires of a standard length are longer than the non-steerable devices with which they are used to permit independent movement of the device and the wire.
Angioplasty is one interventional procedure where a guidewire is often used. In angioplasty a dilatation catheter having an inflatable balloon structure is used to compress occlusive or blockage material against the sides of a vessel, thereby permitting (ideally) circulation to be reestablished. In preparatory procedures, the site of a vascular restriction, occlusion or stenosis is identified. In the usual procedure, the guidewire is inserted into the patient's femoral artery and maneuvered or steered to the location of the restriction. Maneuvering of the guidewire is facilitated by a video X-ray device which allows the physician to observe the movement of the guidewire's distal tip. The guidewire distal tip generally comprises a radiopaque metal to enhance X-ray viewing. A dilatation catheter then is inserted over the guidewire so that its working segment is located adjacent the restriction. Generally this means that the catheter balloon is positioned adjacent the vascular restriction or blockage.
During a simple angioplasty procedure, the dilatation catheter balloon is inflated to open the restriction, and then is removed along with the guidewire. However, complications sometimes arise which prevent the physician from completing this simple procedure. Occasionally the balloon catheter malfunctions. Sometimes a larger (or smaller) balloon is required further to dilate the vascular restriction, or another device or other type of catheter is needed to remove vascular material. For whatever the reason, the guidewire extension system of this invention is used when the catheter, or other such device, has to be removed and replaced with another device or catheter.
In the usual procedure to exchange catheters, the guidewire is removed from the patient, leaving the catheter in the vascular system. An exchange wire is inserted through the catheter and the catheter removed, leaving the exchange wire in place. The new catheter is inserted over the exchange wire and the exchange wire removed and replaced with the guidewire.
It is desirable to keep the guidewire in the patient's vasculature for various reasons. One reason is that the initial placement of the guidewire requires extensive, time consuming, manipulation. Removal and repositioning of the guidewire would be equally time consuming, possibly requiring a patient to be exposed to additional drugs, radiation, and, in general, infliction of additional trauma to the patient. It is also of importance that once the guidewire has been steered to a position across a lesion, that the crossed lesion position not be lost by removal of the guidewire. Guidewires removed from a crossed lesion may induce spontaneous vascular restriction or closure making repositioning of the guidewire difficult if not precluded.
In those cases where catheter exchange is desired, the physician would simply prefer to remove the catheter over the guidewire, leaving the guidewire positioned in the patient. However, to permit catheter exchange, a guidewire over which a catheter is to be exchanged must be sufficiently long to allow the physician to grip a portion of the wire as the catheter is being withdrawn over the guidewire. This requires the guidewire to be long enough to provide an external portion longer than the catheter in addition to the guidewire portion remaining in the patient.
Unfortunately, a guidewire of sufficient length to provide suitably long external and internal portions has inferior handling characteristics, thereby making more difficult the steering and maneuvering manipulations needed for guidewire placement. The added length also imposes itself on the usually cramped vascular suite thereby causing distractions from other support activities. It is for these reasons that guidewires are usually only slightly longer than balloon catheters, e.g. 20-50 centimeters longer, and that a much longer exchange wire is used only with exchange procedures.
Illustrating the above, a dilatation catheter has a shaft length in the range of about 120 cm to about 150 cm, a suitable guidewire for such a catheter would have a length in the range of about 150 cm to about 180 cm and an exchange wire would have a length in the range of about 260 cm to about 300 cm. As can be imagined from the above, utilization of an exchange wire in an exchange wire procedure is complicated and time consuming. This invention simplifies catheter exchange and eliminates the need to use an exchange wire.
A recent development involves coupling or connecting a second length of wire, sometimes called an extension wire or secondary wire, to the exposed, proximal end of a positioned guidewire. The secondary wire length should be sufficient to allow the catheter to be withdrawn while leaving the primary or lesion crossing guidewire in the patient. Various approaches have been suggested for effecting the attachment of an extension wire to a guidewire.
In one approach, such as that described in U.S. Pat. No. 4,922,923 to Gambale et al., a guide wire and an extension are joined together by crimping. A special crimping tool is disclosed in the Gambale et al., '923 patent. A drawback of this approach is that once the wires have been crimped, the connection therebetween is substantially permanent, and the extension wire cannot be detached from the guidewire except by severing it, e.g., by cutting.
Instead of crimping the guidewire to the extension wire, attempts have been made to engage the extension wire to the guidewire frictionally. Such attempts are described, for example, in U.S. Pat. No. 5,113,872 to Jahrmarkt et al., and related U.S. Pat. No. 5,117,838 to Palmer et al. These two patents disclose a guidewire extension system in which the distal end of the extension wire comprises a small diameter tube in which there is disposed a small diameter, open pitch, flat wire coiled spring. The proximal end of the guidewire has a reduced diameter portion which is inserted into the tube assembly to complete the connection. The reduced diameter proximal end of the guidewire is slightly larger than the internal diameter of the coiled spring of the extension wire, thereby creating a frictional engagement when one is inserted into the other. Palmer et al. disclose the utilization of a swivel joint for minimizing twisting of the extension guidewire when connecting or disconnecting it from the extension wire. A device as described in these two patents would be very difficult to manufacture reliably and apparently requires an alignment tool to ease insertion.
U.S. Pat. No. 4,875,489 to Messner et al., discloses an extendable guidewire in which concentric tubular segments are secured to one or the other of the sections to be connected. The inner tubular segment has a longitudinal slot therein which permits it to expand when a cooperating male portion is inserted therein. The outer tubular member of the connector assembly restricts the expansion of the inner tubular member as the male portion is inserted therein.
U.S. Pat. No. 4,846,193 to Tremulis et al., disclose a guidewire having first and second telescopically extendable sections movable between axially extended and retracted positions. No disengagement of the guidewire and extension wire is disclosed.
U.S. Pat. No. 4,966,136 to Kraus et al., discloses an internally threaded female connection member secured to the distal end of the extension wire. The internally threaded female connection member is disclosed to be freely rotatable with respect to the extension wire with securement thereto by means of a collar. The body of the extension wire has a distal enlargement which cooperates with the collar to permit it to be freely rotated. The female connection member of the extension wire cooperates with a threaded male portion located on the proximal end of the guidewire. The mechanism disclosed by Kraus et al., requires the difficult step of threading the segments into each other. Threading pieces having the diameters of a guidewire and an extension wire into each other can be difficult to accomplish, especially under operating room conditions.
U.S. Pat No. 4,827,941 to Taylor et al. discloses a guidewire-extension system employing a tubular female connector portion on one wire and a cooperating male portion on the other. The connecting male portion has an effective diameter in one radial dimension which is slightly larger than the inner diameter of the tubular portion. In a preferred practice, the male end portion of the Taylor et al. guidewire has an undulating shape, which, when inserted into the tube creates an interference friction fit.
U.S. Pat. No. 5,247,942 to Prather et al. discloses a guidewire with a swivel. The Prather et al. invention provides for permanent connection of a main part and an extension part. A swivel is included in the system to permit the permanently affixed parts to be rotated with respect to each other to enhance steerability of the main or guidewire segment. The Prather '942 structure has the same drawback as the Gambale '923 system discussed above.
U.S. Pat. No. 5,246,009 to Adams discloses a complicated guidewire assembly utilizing an inner core wire and an outer tube. Torque transmission is an aspect of the Adams invention.
U.S. Pat. No. 5,271,415 to Foerster et al. describes a guidewire extension system comprising a tubular outer body with guidewire and extension wire elements, e.g., helically wound wires, therein. The device of Foerster et al. has the same disadvantage as that of the Kraus et al. '136 patent, i.e., the interconnect step requires threading of the parts into each other. Moreover, the device described by Foerster et al., with brazed wires inside a tubular structure, may be difficult to manufacture.
The guidewire extension systems discussed above all have one or more drawbacks. Some are difficult or tedious or intricate to engage and disengage. Others do not disengage at all. While frictional engagement overcomes the disadvantages of crimping, disengagement may occur too easily. Problems of discontinuity at the guidewire/extension wire connection e.g., kinking, have been experienced with some systems. Moreover, prior extendable wires for use in coronary angioplasty procedures have been found to be unsuitable in peripheral arteries because the connections are not sufficiently strong. Further, some connections have larger diameters than the rest of the guidewire system. This may cause snagging of, e.g., over the wire catheters. It also means that the catheter with which such connection system is used must have a larger internal diameter lumen than would be necessary were a smaller diameter coupler employed.
Accordingly, a principal object of the present invention is to provide a guidewire extension system which is reliable, easy to use and easy to manufacture.
Another object of the present invention is to provide a guidewire extension system which does not require that either the guidewire or extension wire be rotated when attaching one to the other. It is advantageous that the guidewire be held stationary because the guidewire is located within the patient's blood vessel where unnecessary movement can induce trauma. It is also advantageous to have the majority of the length of the extension wire held stationary (e.g., by retention within a carrier structure) during the connection process. Having the extension wire self-contained in a tubular carrier package allows medical personnel to concentrate upon engaging the two wires using the present extension system. An uncontained extension wire is awkward, and thus complicates the process of effecting a guidewire/extension wire union during a medical procedure.
It is a further object of this invention to provide an easily attachable (and reattachable) and easily detachable guidewire extension system which has a readily identifiable tactile sensation, e.g., a "snap", when the system components are affirmatively attached.
It is still a further object of the present invention to provide a guidewire extension system which has substantially the same flexibility and pushability at its connection as that of the remainder of the length of the guidewire. The system provides an advantageously controllable coaxial alignment of the guidewire and extension wire.
It is yet another object of the present invention to provide a unitized guidewire extension system having a substantially uniform, smooth, continuous outer diameter or profile along the guidewire, connector, and extension wire. A smooth, continuous transition in external profile from the distal end of the guidewire to the proximal end of the extension wire, especially over the connector segment, permits an over-the-wire catheter to be positioned without becoming hung up. Methods of manufacturing an extension system of this invention and methods of using a system of this invention also are disclosed.